With an increase in the recording density of an optical disc, there has been increased a demand for the performance of a transfer apparatus for performing a sled transfer (sliding transport) for an optical pickup. For example, a blue-ray disc (BD) for recording and reproducing an optical disc by using a blue laser has a track pitch of ½ or less of a digital versatile disc (DVD). Accordingly, it is desirable that the feeding accuracy of an optical pickup for the blue-ray disc should also be set to be ½ or less than that of an optical pickup for the DVD. If the setting is to be implemented with an enhancement in mechanical precision, a cost is greatly increased.
A mechanism for converting the rotation of a motor into a linear motion by means of a gear or a feed screw is used for transferring the optical pickup. However, a gear to be used in the transfer apparatus has a backlash, thereby bringing a state in which the optical pickup is not transferred even if the feed screw is rotated. Such a non-transfer state has become an important factor of a deterioration in an accuracy. Moreover, a dead zone is caused by the backlash so that a control performance such as a follow-up delay is deteriorated. Accordingly, a high machine accuracy has been required for the gear in order to reduce the backlash, or a mechanism for performing pushing by means of a spring has been required to be additionally provided. Alternatively, a plurality of guide shafts has been provided or there has been devised the shape of an elastic support portion for elastically coupling a pickup support portion to a rack portion or a feed screw portion (see, Japanese Patent Application Kokai No. 2003-263848).
More specifically, a conventional transferring mechanism of a pickup device is capable of decreasing the influence of a backlash to suppress a vibration and a delay. However, the conventional transferring mechanism has a problem in that a machine accuracy is required or a structure becomes complicated, resulting in an increase in a cost when a high performance is to be obtained. In the conventional technique, furthermore, a method of increasing the elastic support force of an elastic support portion for elastically coupling a pickup support portion to a rack portion or a feed screw portion is used as a method of suppressing a mechanical backlash in some cases. In these cases, however, a drawback such as a loss of synchronism is caused by an increase in a driving load. In the worst case, there has also been a problem in that a transfer operation as an original object cannot be carried out.